Blog about bats in the garden

Allthough most people know me from aquatic and tree surveys 2018 was the year of the bat.

Bats are shy and unknown to many people. Depending on your cultural background you might associate them with Halloween and scaring people or, on the positive side with Wu-Fu, Chinese symbol of the five great happiness’s: health, wealth, good luck, long life and tranquillity. Being nocturnal their live takes place when we go to bed. Often we are not aware if they are visiting our garden like a robin or blue tit does. All bats in the UK are insectivorous and use echolocation to find their prey.  
All bat species, their breeding sites and resting places are fully protected by law - they're European protected species.They largely feed on airborne insects, suppress both naturally occurring and human related-generated insect populations (such as agricultural pest species and insects that annoy or transmit specific pathogens to humans and other mammals) and contribute to the maintenance of ecosystem stability. They are good in finding concentrations of insects. Most feed on moths in June but smaller species on little bugs and mosquitos as well. They can eat over a three thousand at one night.
Since 60% of insects are nocturnal as well you might understand their importance. Evolutionary seen they are very special as well. They are the only mammals that are capable of self-powered flight. With over 1200 different species they represent a fourth of all mammals species known in this world. They have developed many niches in for example in foraging, hibernation, flight, required habitat and roosts. Although very adaptable on an evolutionary scale most species can’t keep up with urbanisation taking place in this world.
Summer 2017 I started to study Ecological Survey Techniques at Oxford University to expand my survey and research skills. As part of this study I did a field survey studying bat presence and prey availability in the urban environment. The study will look at the elements we can influence as human beings and the role of our gardens for bats in expanding cities.
Conclusions from my study:
Bats were present across all sites although diversity was low, especially in activity level, and dominated by only two species; P. pipestrellus and P. pygmaeus.  All results, except for woodland, were directional and only large trees, distance to water and prey availability showed a significant increase in bat activity. Highly specified and mobile species require a large set of spatial distribution data, preferably permanently monitored over a season.  Quality species-specific distribution maps are with this sample size not possible. The attempt to make a garden suitability index that can be used for further testing in a wider context proved for the above reasons overambitious.

At the sampled gardens, prior to this survey, only six owners were aware that their garden was visited by bats. Most were unaware that (garden) lighting causes ecological shifts in diurnal and nocturnal species. They might have seen P. pipestrellus species feeding near light but did not know most other bat species are deterred from light. The survey provided the opportunity to share information about the importance of trees and varied vegetation height. It created for many their first bat sighting or hearing experience ever. Although not the purpose of the study a shift in appreciation of bats and the eco-services they provide is required to gain support for maintaining important habitat features.

You could have a little science self-build project with your kids over the holiday. More information: The bat Conservation Trust and  brochure in bat friendly gardening and living.

Bats are a bit picky. They don’t like strong winds, cold nights and heavy rain. A bit like most of us they prefer to stay inside and make that evening unsuitable for surveying. If the nights get warmer (10 C°+) they will come out of hibernation as soon as the sun sets. 

Lonneke Klein-Aarts